1. Field of the Invention
This invention relates to a network protector bus clamp and, more specifically, to a network protector having a removable bus clamp assembly that may be removed from the bus without disassembling the clamp.
2. Background Information
Secondary power distribution networks consist of interlaced grids which are supplied by two or more sources of power so that the loss of a single source of power will not result in an interruption of service. Such secondary power distribution networks provide the highest level of reliability possible with conventional power distribution and are normally used to supply high-density load areas such as a section of a city, a large building, or an industrial site. Between a power source and the network is a transformer and a network protector. The network protector consists of a circuit breaker and a control relay. The circuit breaker includes at least one set of main contacts that move between an open position and a closed position. When the main contacts are closed, electricity may flow through the network protector. The control relay senses the transformer and network voltages and line currents and executes algorithms to initiate breaker tripping or closing action. Trip determination is based on detecting an overcurrent condition or reverse power flow, that is, power flow from the network to the energy source. Network protectors are often found in dust-proof or moisture-proof housings, or vaults, which are disposed in subterranean passageways in large metropolitan areas.
The network protector circuit breaker has at least one line bus and a load bus. Typically, the circuit breaker is a three phase circuit breaker having three poles, each with a line bus and a load bus. The network protector busses are coupled, respectively, to a vault line bus and a vault load bus. Either the vault line bus or the vault load bus will include a fuse located on the line opposite the clamp. The network protector circuit breaker bus that is coupled to the vault bus having the fuse uses a clamp assembly to couple the network protector circuit breaker bus to the vault bus. The vault bus also terminates in a coupling block. The clamp assembly includes a plurality of gripping fingers that are structured to move between a closed position, wherein the clamp assembly engages the coupling block, and an open position, wherein the clamp assembly does not engage the coupling block. When the clamp assembly is not engaging the coupling block, and after other connections are separated the circuit breaker may be rolled out of the vault. After the repair or maintenance operations are complete, the circuit breaker is moved into the vault and the fingers are moved into the closed position, gripping the coupling block.
It is a priority for utility companies, and other users, to reduce the down time of the network protector during repair. One way to reduce the down time is to simply replace the network protector. The difficulty in replacing a network protector is that the replacement unit must have a clamp assembly that is structured to interact with the vault bus in the vault that houses the network protector. The shape of the vault busses vary depending on whether the bus fuse is located on network side or the transformer side of the circuit breaker. Additionally, prior art clamps were designed to be attached to five inch tubular bus sections. Current network protectors have laminated rectangular busses which are about two inches thick. Moreover, the prior art bus clamp must be completely disassembled during the removal procedure. That is, the mounting assembly for the clamp assembly must be engaging the network protector bus to hold the clamp assembly together. As such, to remove the clamp assembly, the clamp assembly must be disassembled during the removal procedure and reassembled during the installation procedure. The disassembly and reassembly of the clamp assembly causes delay in the maintenance and/or repair procedure.
There is, therefore, a need bus clamp assembly that is structured to engage a laminated bus.
There is a further need for a bus clamp assembly that can be easily removed from, and reinstalled on, a laminated bus.
There is a further need for a bus clamp assembly that is compatible with existing equipment.
These needs, and others, are satisfied by the invention which provides a bus clamp assembly having a mounting bracket that is structurally separate from, but coupled to, a gripping assembly. The gripping assembly provides the clamping function for attaching the network protector bus to the line conductor or the load conductor. The mounting bracket attaches the clamp assembly to the network protector bus. The bracket may be attached or removed from the network protector bus without disassembling the gripping assembly.
The mounting bracket is an L-shaped body having a first leg and a second leg. The first leg has a plurality of openings. The first leg openings are structured to align with openings on the network protector bus. As such, a fastening device, e.g. bolts, may be passed through the first leg openings and the network protector bus. Nuts are coupled to the bolts thereby attaching the bracket to the bus. The second leg of the bracket has one or more openings as well. The second leg opening cooperates with a fastening device to couple the bracket to the gripping assembly. The fastening device passing through the second leg and coupling the bracket to the gripping assembly remains in place as the first leg fastening devices are removed or installed. As such, the griping assembly does not have to be assembled or disassembled as the clamp assembly is coupled or de-coupled from a network protector bus.